The Wall Street Journal reports on a new study of productivity, accessibility, and worker effectiveness:

Reading and sending work email on a smartphone late into the evening doesn’t just make it harder to get a decent night’s sleep. New research findings show it also exhausts workers by morning and leaves them disengaged by the next afternoon.

That means the way most knowledge workers do their jobs—monitoring their iPhones for notes from the boss long after the office day is done and responding to colleagues at all hours—ultimately makes them less effective.

The researchers conducted two studies. The first was with 82 managers who "were asked every morning how many minutes they used their smartphone after 9:00 pm the night before and how many hours they slept," and surveyed about their attitudes and energy level. The second study "measured how late-night tech use—on smartphones, laptops, tablets and TV—can disrupt sleep and next-day work engagement" for 161 workers.

The study, "Beginning the workday yet already depleted? Consequences of late-night smartphone use and sleep," is available behind the Science Direct firewall. I confess I haven't read it really closely, but it certainly looks impressive. Here's the abstract:

Smartphones have become a prevalent technology as they provide employees with instant access to work-related information and communications outside of the office. Despite these advantages, there may be some costs of smartphone use for work at night. Drawing from ego depletion theory, we examined whether smartphone use depletes employees’ regulatory resources and impairs their engagement at work the following day. Across two studies using experience sampling methodology, we found that smartphone use for work at night increased depletion the next morning via its effects on sleep. Morning depletion in turn diminished daily work engagement. The indirect effects of smartphone use on depletion and engagement the next day were incremental to the effects of other electronic devices (e.g., computer, tablet, and television use). We also found some support that the negative effects of morning depletion on daily work engagement may be buffered by job control, such that depletion impairs work engagement only for employees who experience low job control.